Did you know that there is a - not so common - form of dementia whose symptoms can be improved with neurosurgical intervention?

This concerns Normal Pressure Hydrocephalus (NPH).​

Definition and Pathophysiology

Normal pressure hydrocephalus (NPH) is a pathological condition in which the volume of cerebrospinal fluid (CSF) increases in the brain's ventricles, while intracranial pressure typically remains at the upper limits of normal, due to slow and gradual accumulation. CSF is normally produced at a rate of 125-150 ml in adults, with intracranial pressure of 15-20 cmH₂O; in NPH, the balance of production, flow, or absorption is disrupted. This ventricular enlargement compresses the brain from inside outwards, causing neurological dysfunction without acute hypertension.​

Symptoms and Clinical Picture

The classic triad of symptoms includes gait disturbance (unsteady, broad-based gait), cognitive impairment (executive dysfunction, memory weakening), and sphincter dysfunction (urinary incontinence). It often presents in the elderly, mimicking dementia such as Alzheimer's, with progressive deterioration if untreated; gait disturbance is frequently the first symptom, followed by incontinence and dementia.​

Causes and Risk Factors

It arises from impaired CSF absorption, often idiopathic in the elderly or secondary to head trauma, haemorrhage, infection, or obstruction. It is associated with falls, subdural haematomas, or intracerebral haemorrhages, particularly in individuals over 60 years old, with slow progression allowing maintenance of normal pressure.​

Diagnosis

Diagnosis relies on imaging (CT/MRI showing ventricular enlargement), neuropsychological assessment, motor evaluation (e.g., gait ability), and CSF drainage testing (tap test). Improvement in neuropsychological and motor abilities after adequate CSF drainage (at least 40-50 ml) confirms the diagnosis; a thorough neurological evaluation is recommended to exclude other dementing pathologies.​

Treatment and Prognosis

Surgical placement of a ventriculoperitoneal (VP) shunt from the brain ventricles to the peritoneum is the primary treatment, improving symptoms in many patients if performed early. Typically, urinary symptoms improve first, followed by gait, and finally memory.

Photo resource: Singh G, Sharma R, Gaillard F, et al. Normal pressure hydrocephalus. Reference article, Radiopaedia.org (Accessed on 08 Dec 2025) https://doi.org/10.53347/rID-6306